1. Field of the Invention
The present technology relates generally to auditory prostheses and, more particularly, to such prostheses having a common, and two or more stimulator-specific, frequency-analysis stages.
2. Related Art
Hearing loss, which may be due to many different causes, is generally of two types, conductive and/or sensorineural. Conductive hearing loss occurs when the normal mechanical pathways of the outer and/or middle ear are impeded, for example, by damage to the ossicular chain or ear canal. Sensorineural hearing loss occurs when there is damage to the inner ear, or to the nerve pathways from the inner ear to the brain.
Individuals suffering from conductive hearing loss typically receive an auditory prosthesis that provides acoustic stimulation, e.g., an acoustic hearing aid. Hearing aids rely on principles of air conduction to transmit acoustic signals to the cochlea. Typically, a hearing aid is positioned in the ear canal or on the outer ear to amplify received sound. This amplified sound is delivered to the cochlea through the normal middle ear mechanisms resulting in the increased perception of sound by the recipient. It is worth noting that hearing aids are commonly referred to as hearing instruments by the industry and the electro-acoustic transducer (commonly referred to as the receiver) is a speaker that outputs sound to the recipient, i.e., the receiver is not the microphone.
Individuals who suffer from conductive hearing loss typically have some form of residual hearing because the hair cells in the cochlea are undamaged. As a result, individuals suffering from conductive hearing loss might receive an auditory prosthesis that provides mechanical stimulation, e.g., generates mechanical motion of the cochlea fluid. Such prostheses include, for example, bone conduction devices and direct acoustic stimulators.
In many people who are profoundly deaf, however, the reason for their deafness is sensorineural hearing loss. Those suffering from some forms of sensorineural hearing loss are unable to derive suitable benefit from auditory prostheses that generate mechanical motion of the cochlea fluid. Such individuals can benefit from an auditory prosthesis that provides electrical stimulation, e.g., that stimulates nerve cells of the recipient's auditory system in other ways (e.g., electrical, optical and the like). Cochlear implants are often proposed when the sensorineural hearing loss is due to the absence or destruction of the cochlea hair cells, which transduce acoustic signals into nerve impulses. Auditory brainstem implants might also be proposed when a recipient experiences sensorineural hearing loss if the auditory nerve, which sends signals from the cochlear to the brain, is severed or not functional.
More recently, there has been an increased interest in auditory prostheses that are capable of using multiple types of stimulation to stimulate the recipient and thereby evoke a hearing percept. Using multiple types of stimulation provides a recipient with the ability to perceive a wider range of frequencies regardless of the cause of hearing loss. Example combinations of stimulation types in such auditory prostheses include (1) electrical stimulation and acoustic stimulation, (2) bone-conductive mechanical stimulation and middle-ear mechanical stimulation, (3) bone-conductive mechanical stimulation and acoustic stimulation, (4) electrical stimulation and middle-ear mechanical stimulation, etc.